With attachment redirection option ON, attachment pages are not reachable, but redirected to perent posts … but still they are present in attachment-sitemap.xml …. My guess is that this sitemap is not needed with this option ON, or am I wrong?

I am still not sure if i need this option turned on, or its better to leave attachment pages reachable, couse all my pictures are filled in with descriptions etc, so SEO friendly, i guess… any tips ?